The present invention relates to an electronic copying machine for making a hard copy of a remote surface such as a writing board.
In recent years, there have been developed electronic copying machines capable of making a hard copy of notes, illustrations or the like written on a writing board itself or on a sheet placed on or tacked to the writing board, which consists of a video camera and a printer assembled as an integral unit. In one such electronic copying machine, an image of a selected part of the remote surface is optically formed on an image sensor, such as a charge coupled device (CCD), of the video camera and converted into video signals. A printing head of the printer is driven by the aid of or according to the video signals to print an image on a copy paper. Such electronic copying machines are often used on a table or desk. Because tables or desks and writing boards are usually different in height, an electronic copying machine on a table is not always capable of forming an image of the whole surface of the writing board.
To make it possible to cover the whole surface of the writing board, it was proposed that the electronic copying machine be placed on a table in such a way as to incline the optical axis of the image-forming optical system upward at a proper angle with respect to the surface of the writing board. This, however, leads to the so-called keystone effect in the copied image. That is, the image of the surface of the writing board formed by the electronic copying machine thus placed on the table has disproportionate vertical magnification relative to horizontal magnification. To eliminate this keystone effect, the electronic copying machine should be displaced vertically so as to dispose the optical axis of the image-forming optical system perpendicular to the surface of the writing board. This leads to a troublesome adjustment of the electronic copying machine on the table with respect to the writing board.
In an attempt at avoiding the need for such a troublesome adjustment, a novel electronic copying machine has been proposed in Japanese Utility Model Appln. No. 62-202,873 now U.S. Pat. No. 4,939,533 filed by the assignee of the present application. The electronic copying machine described in this Japanese utility model application consists of a main housing containing a printing unit and a roll of copy paper on which images are printed, and an image-forming unit having at least an image-forming optical system, such as a taking lens system, and an image sensor enclosed in an image-forming unit housing. The image-forming unit housing is supported by a supporting post or structure mounted on the main housing for pivotal movement. In advance of making a copy of the remote surface such as the surface of a writing board, the supporting post is pivotally raised so as to position the optical axis of the taking lens system perpendicular to the center of an area of the remote surface to be copied.
Because the image-forming unit housing is affected by mechanical vibrations from the printing unit and other moving parts, which vibrations are amplified and transmitted through the raised supporting post, an image produced by the image-forming unit will often be unclear or blurred.